Sriram R. Ramaswamy

Sriram Ramaswamy works on soft-matter and nonequilibrium physics. He laid down the defining principles of the field known as Active Matter, the study of materials whose constituents, such as cells in a tissue, continually convert a free-energy supply into work. His achievements include: a hydrodynamic theory of suspensions of motile entities as a strange kind of liquid crystal, whose successful predictions include the instability of slow flocks in fluid and the dramatic modification of viscosity by swimming stresses; design rules for artificial realizations of flocking and chemotaxis; the insight that certain defect structures in active liquid crystals must self-propel, resulting in the defect-unbinding theory of the melting of active nematics; the demonstration that a trace concentration of motile particles can herd or condense passive matter on large scales; and the theory of fluctuations and instabilities of fluid membranes with active force centres. Decades before its current revival in an active-matter context, nonreciprocal dynamics featured prominently in Sriram's theory of drifting lattices, including waves without mechanical inertia, phase separation in one dimension with bounded local interactions, and an exceptional-point phase transition. Other key works include the broken-symmetry hydrodynamics of quasicrystals, anomalies in one-dimensional heat conduction, insights into the glass transition, and the singular enhancement of viscosities in smectic liquid crystals.